[parser] add drop column with index flag (#1286)
[parser] add drop column with index flag (#1286)

Signed-off-by: ailinkid <172c35aafe80d50c8cec5d18d3df3574d9075f55@qq.com>
kyle-wang/tidb,c4pt0r/tidb,pingcap/tidb,c4pt0r/tidb,ngaut/tidb,coocood/tidb,kyle-wang/tidb,ngaut/tidb,ngaut/tidb,c4pt0r/tidb,kyle-wang/tidb,pingcap/tidb,kyle-wang/tidb,coocood/tidb,ngaut/tidb,pingcap/tidb,kyle-wang/tidb,c4pt0r/tidb,ngaut/tidb,c4pt0r/tidb,pingcap/tidb,ngaut/tidb,kyle-wang/tidb,pingcap/tidb,c4pt0r/tidb,pingcap/tidb